Business owners in parts of the devastated city of New Orleans are being allowed back into the area to start clean-up and begin readying for re-opening.

New Orleans Mayor Ray Nagin has called on business owners to return to the French Quarter and some other parts of the city -- but other officials are warning there may be limited or no electricity or clean running water.

Some residents will also be allowed to return to their homes Monday.

Less than half of New Orleans remains flooded, but dangers from downed power lines, natural gas leaks, toxic debris and other hazards remain.

Hurricane Katrina ravaged the U.S. Gulf Coast on August 29. The death toll in five states is now more than 800.